<!DOCTYPE html>
<html lang="zh">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .father > p {
      color: red;
    }
  </style>
</head>

<body>
  <!-- 只让小可爱变红 -->
  <div class="father">
    <p>小可爱</p>
    <div>
      <p>小姐姐</p>
    </div>
  </div>
  <p>大可爱</p>
</body>

</html>